In modern C++, what is the neatest way to refer to the "this" class?

Question

With template classes and template bases it becomes complicated to nominate the types, I often add private typedefs such as Base and This for use later:

template<typename T>
class A : public B<Something<T>> {
private:
    typedef B<Something<T>> Base;
    typedef A<T> This;

public:
    // .......

Q: is there a way to "get" This without defining it? This would seem like a very unambigous requirement, but maybe it's not.

I'm asking for C++17, but useful to know for later dialects as well.

In case you need a use-case, I am using This in a construct like the following (which is itself a workaround for something else):

private:
    auto somethingComplicated() const {
        return std::make_tuple(.........);
    }

    decltype(std::declval<This>().somethingComplicated()) field = somethingComplicated();

For `This` see [Injected-class-name - In class template](https://en.cppreference.com/w/cpp/language/injected-class-name) — Richard Critten, May 30 '22 at 08:41
your example isnt really showing the issue of "getting complicated". Actually `A` (or even `A`) would be shorter and more clear than using `This`. — 463035818_is_not_an_ai, May 30 '22 at 08:49
I think I wasn't explicit enough that I'd like a method invariant of the actual class name. To give another example, think of a construct that you could use from within a macro invoked at class scope. The macro is even allowed to define members to this purpose. — haelix, May 30 '22 at 08:49
hence what you put in the macro should work without knowing that the class is named A etc — haelix, May 30 '22 at 08:51
if the macro needs the type of the class then it needs the type of the class. No magic can help with that — 463035818_is_not_an_ai, May 30 '22 at 09:01
this is a duplicate for the question you didnt ask https://stackoverflow.com/questions/1666802/is-there-a-class-macro-in-c — 463035818_is_not_an_ai, May 30 '22 at 10:01
Unfortunately `decltype(*this)` only works inside methods. Even `auto declmethod() { return *this; }` doesn't help because you can only write `decltype(declmethod())` inside other methods. If you had an `A*` to call `declmethod` on, you could just call `decltype` on that `A*`. — MSalters, May 30 '22 at 10:19

In modern C++, what is the neatest way to refer to the "this" class?

0 Answers0